Alternatives to graphite in EV batteries

Graphite makes up the bulk of the anode (95%) of a typical Li-ion battery mounted in a battery powered electric vehicle (BEV) and requires approximately 1 kg of graphite per kWh of battery energy, making it, by weight, the most important is element of the battery cell.

China has achieved a dominant position in the supply of the type of high-quality processed graphite needed for BEV batteries, with estimates suggesting it accounts for about 85% of the global supply. Not only does it have significant reserves of natural graphite, but it also has a near monopoly on the industrial processes needed to convert the material from the mined (“flake”) state to the high-purity spherical graphite needed to power the battery anode. to shape.

There is an alternative to natural graphite, which is synthetic graphite made with petroleum as the raw material. In fact, battery cell manufacturers prefer synthetic graphite because its more uniform structure is conducive to longer battery life. Estimates indicate that natural graphite has caught up with current BEV Li-ion battery production and anodes are often made from a mixture of natural and synthetic graphite. There’s a catch, or two. It is also more expensive than natural graphite and even less environmentally friendly than natural graphite in its procurement and production methods. And coincidentally, China also dominates the global supply of synthetic graphite.

The chart shows how demand for battery-grade graphite for the BEV sector would grow this decade, assuming it remained the sole anode material.

Only recently, driven by the projected growth in demand for graphite from the battery vehicle sector, have projects capable of supplying battery-grade graphite on a large scale been launched outside of China. Australia is a focus, but projects are being developed in Canada, Alaska, Africa and in Europe. Rising demand for graphite makes these projects viable, but also increases the price of battery-grade graphite, especially when produced in areas where refining by-products are more tightly controlled (than in China).

These issues of cost, battery performance (is there a better alternative to graphite?), ESG concerns and security of supply have led to a long search for alternatives to graphite as anode material.

Perhaps the main driver is battery performance, although the increasing pressure on the graphite industry and its dominance by China should not be ignored. Although Li-ion batteries have (until recently) come down in price, the speed at which their performance can improve has decreased with current technologies. At the same time, the industry has massively focused on the production of Li-ion batteries rather than any other type. A lot of work has gone into changing cathode chemistry, be it improving performance (range and charging time) or avoiding the use of controversial materials (such as cobalt). But there are limitations and trade-offs in what can be achieved. It’s a bit like buying a new home: you can have space, location, or affordability, but you can’t have all three at once. With conventional Li-ion batteries it is a trade-off between energy storage, durability and weight/size of the packaging.

It has long been known that using silicon as an anode material can significantly improve energy density – silicon can store many more lithium atoms than graphite. Nowadays even up to 10% silicon is mixed with graphite anodes for this purpose. However, the disadvantage of pure silicon anodes has always been the tendency of silicon to expand and contract during the charge and discharge cycle (up to 300%), leading to premature cell failure. The problem to be solved, therefore, was to create a silicon-based material that would provide the energy storage benefits of silicon versus graphite, while remaining stable over thousands of charge/discharge cycles. This now appears to have been achieved, with companies such as US-based Sila Nanotechnologies (Sila) leading the way. The scaling up of production of such anode material has reached a point where Mercedes-Benz has specified a silicon anode battery from Sila for its forthcoming all-electric G-Wagon.

This appears to be a major breakthrough, with early adoption at the heavier end of the electric vehicle spectrum, where the improved energy density is helping to reduce increasingly heavy and bulky batteries.

Coming back to the trade-off point made earlier, what this new anode material does is significantly reduce the amount of battery weight/size that has to be gained to get a higher capacity battery. As for cost vs graphite, this is yet to be fully revealed, but we can assume that given the small scale of silicon anode production as the industry grows, it could be higher than a graphite cell at first. But the raw material is plentiful and cheap (silicon is the second most abundant element in the Earth’s crust after oxygen), so the cost will largely depend on the scale of the industrialization process.

Finally, an important point is that replacing graphite with silicon does not mean that cell manufacturers have to drastically reconfigure their Li-ion gigafactories. Given the huge investments being made in the sector, that’s a good thing.

Al Bedwell

This article was first published on GlobalData’s dedicated research platform, the Automotive Intelligence Center

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